Shrinkproofing of wool by low temperature plasma treatment

ABSTRACT

Method and apparatus for shrinkproofing fibrous material of animal origin-e.g., wool, mohair, and the like-wherein the fibrous material is subjected to a low temperature plasma created by a high-frequency electrical discharge.

[451 July 17, 1973 SHRINKPROOFING OF WOOL BY LOW TEMPERATURE PLASMA TREATMENT Inventors: Attila E. Pavlath; Richard F. Slater,

both of Berkeley, Calif.

Assignee: The United States of America as represented by the Secretary of Agriculture, Washington, DC.

Filed: Dec. 21,1971

Appl. No.: 210,419

Related U.S. Application Data Division of Ser. No. 60,446, Aug. 4, i970.

[56] References Cited UNITED STATES PATENTS 3,057,792 10/1962 Frohlich 250/495 X 3,179,482 4/1965 Kassenbeck 250/495 X 2,977,475 3/l96l Kassenbeck 250/495 Primary Examiner-William F. Lindquist Attorney-R. Hoffman et al.

[57] ABSTRACT Method and apparatus forshrinkproofing fibrous material of animal origine.g., wool, mohair, and the like-wherein the fibrous material is subjected to a low U.S. c1. ..250/325, 317/4 temperature plasma created by a high frequency 61w 1 t. 003 15/02 Field of Search 250/495 oc, 43.5 TC;

317/4, 262 A 1 Claim, 2 Drawing Figures R. F. M5 G E N E R ATOR To Monometer 3 6 9 I24 {1 l2 9 GITX O O (5 U02 I O k I O l I -44 4 1 8 To l TO VACUUM TO VACUUM PUMP VACUUM PUMP v PUMP Patented Jab 17,19,73- 3,746,858

R.F. V5 I GENERATOR v f To Monometer O 3 3 0 I6 I l M U 4 1 l8 -'1 I TO v VACUUM TO .VACUUM PUMP VACUUM PUMP PUMP fF/G.

VACUUM P TO GAS SOURCE SHRINKPROOFING OF WOOL BY LOW TEMPERATURE PLASMA TREATMENT This is a division of our co-pending application Serial No. 60,446, filed Aug. 4, 1970.

A nonexclusive, irrevocable, royalty-free license in the invention herein described, throughout the world for all purposes of the United States Government, with the power to grant sublicenses for such purposes, is hereby granted to the Government of the United States of America.

This invention relates to and has among its objects the provision of novel methods and apparatus for shrinkproofing fibrous material of animal origin, e.g., wool, mohair, and the like. Further objects of the invention will be evident from the following description and the annexed drawing.

In the drawing:

FIG. 1 is a diagram illustrating a form of apparatus in accordance with the invention.

FIG. 2 is an enlarged cross-section of a portion of the apparatus of FIG. 1.

In the following description the treatment of wool is stressed. It is to be understood, however, that the invention is also applicable-to other proteinous fibrous materials such as mohair, cashmere, alpaca, vicuna, camel hair, and other proteinous fibers derived from animal sources. The materials may be in any of various physical forms, e.g., slivers, rovings, yarns, top, felts, woven or knitted fabrics, etc. Usually it is preferred to treat the fibrous material before it hasbeen fabricated into a cloth. Especially preferred is the treatment of filamentary forms of the textile such as webs, strands, yarns, or the like. Materials treated in accordance with the invention can be used in all the conventional applications of fibrous materials, as in the production of garments of all kinds. As will be explained hereinafter, the treatment of the invention improves the properties of the fibrous materials so that textile products produced therefrom have enhanced properties such as dimensional stability and durability.

A basic step in the process of the invention involves exposing the wool or other proteinous fibers to an electrical glow discharge, or plasma, at a temperature of about 25 to 300 C., preferably no higher than about 150 C. Such a discharge is readily produced, as well known in the electronic art, by applying an alternating current toair or other gas at low pressure (usually 1 to 'l mm Hg). Because of the relatively low temperature of this type of luminous discharge it is commonly referred to as cold" plasma to differentiate it from the hot plasma systems which operate at temperatures on the order of 5,000 to l0,000 K or higher. The glow discharge involves the formation of active forms of the gases present in the system, thus yielding high concentrations of ions and electrons. Because of the high energy of these species and their high concentration, they are able to cause profound chemical and physical changes in fibrous materials exposed thereto. ln particular, it has been found that when wool is exposed to such a discharge, it is advantageously modified, for example, it is made shrink resistant and its tensile strength and abrasion resistance are markedly improved. Our

investigations have shown, for example, that when the products of the invention are washed their shrinkage is only about l/l0 that of untreated wool washed in the same manner. We have also found that the treatment of the invention causes increases in tensile strength and abrasion resistance of from 30 to percent.

An important advantage of the apparatus in accordance with the invention is that it provides an arrangement whereby yarn or other filamentary material can be continuously fed through the system while maintaining the reaction chamber (where the yarn is treated) under low pressure. A feature of our arrangement is that it does not employ any conventional sealing equipment so that the yarn under treatment is not subjected to friction, abrasion, stretching, or other deleterious forces. Moreover, our arrangement is very simple and economical and has the technical advantage that both the supply of starting yarn and the finished product (the treated yarn) are stored in the open air during operation of the process.

The practice of the invention is further explained in connection with the annexed drawing:

Reference numeral 1 designates a reaction chamber made of borosilicate glass, or the like, provided with conduit 2 which is connected to a conventional vacuum pump for maintaining the pressure within chamber 1 at a level of about 1 to 100 mm. Hg. A tube 3 is provided for connection to a manometer so that the pressure in chamber 1 can be measured.

Positioned on the exterior of chamber 1 are a pair of plates 4 of copper or other electrically-conductive metal, which are connected to a radio-frequency generator 5 for creating the plasma within chamber 1. Generator 5 is preferably of the type which produces an alternating current and is equipped with conventional equipment-such as a tuned capacitance matching network-so that a maximum of power (resonant conditions) can be impressed within chamber 1. Preferably,

\ generator 5 is also supplied with a wattmeter capable of reading both forward and reflected power so that the net power going into the system can be measured. lf desired, plates 4 can be replaced by a coil, in which case generator 5 would be equipped with a tuned impedance matching network so that a maximum of power could be applied to the system. The frequency of the current yielded by generator 5. is not critical; generally, radio frequencies or micro-wave frequencies are used. To avoid interference with broadcasting, certain frequencies are allotted by the FCC for devices of this type, namely, 13.56 M Hz, 27.12 M Hz, and micro-wave frequencies between 950 and 5,000 M Hz. All of these are suitable for the practice of the invention. It will be understood that the generator and auxiliary equipment are well known in the artand are available on the market.

For conducting yarn 6 through reaction chamber 1, there are provided capillary inlet tube 7 and capillary outlet tube 8. The internal diameter of these tubes is so selected that the yarn can slide through them readily without being subjected to any friction, abrasion, or stretching. Typically, the internal diameter of tubes 7 and 8 is about 1.1 to 3 times the diameter of the yarn being processed. Since the ends of tubes 7 and 8 are exposed to the atmosphere, a certain amount of air will tend to enter chamber 1 when it is evacuated. This flow of air is impeded, however, by the long and narrow dimensions of tubes 7 and 8, and further by auxiliary means hereinafter explained.

Mounted on tubes 7 and 8 are connectors 9, each of like construction, and each in communication with a pipe 10. These pipes are connected to a conventional source of vacuum, such as a vacuum pump.

Reference is now made to FIG. 2 which shows the in ternal construction of a connector 9. It will be observed that a port 11 is provided in tube 7 so that there is communication between pipe 10 and the interior of tube 7. Thus, when pipes 10 are connected to the vacuum pump, air which enters the system via tubes 7 and 8 is exhausted. It will be obvious that the vacuum pump applied to pipes 10 must be of such capacity that whatever air is not scavenged from tubes 7 and 8 can be handled by the vacuum pump applied to conduit 2. Usually, it is preferred to supply two separate vacuum pumps, one for exhausting chamber 1 and the other for handling the connectors 9.

In the preferred modification of the invention, connectors 9 and auxiliary equipment are provided as above explained. With such a system it is easy to maintain any desired pressure in chamber 1, even low pressures, that is, those below about 25 mm. Hg. Where the system is to be operated at pressures above about 25 mm. connectors 9 and the auxiliary equipment can be dispensed with, and the desired vacuum produced solely by the pump applied to conduit 2. Where this is done, it is preferred to elongate tubes 7 and 8 so that they will offer a greater resistance to the inflow of air.

In some cases it is desired to conduct the treatment in the presence of a selected gas other than air. For this purpose there are provided connectors 12 equipped with pipes 13. Connectors 12 have the same construction as in the case of connectors 9, and there is a bore 15 in corresponding tubes 7 and 8 (note FIG. 2) to provide communication between the tubes and connectors 12. Pipes 13, in turn, are connected to a suitable supply of a desired gas, such as a conventional tank thereof. In the event that ambient air is to be the residual gas in chamber 1, pipes are maintained in a sealed condition by closing valves 14.

In operation of the device, yarn 6 is drawn from bobbin 16 through the system by driven rolls 17. The yarn passes through tube 7 into chamber 1 where it is subjected to the plasma, and then leaves the system via exit tube 8 and is wound up onbobbin 18. The process is carried out continuously until the entire length of yarn on bobbin 16 has been treated. By using bobbins of commercial size, very long lengths of yarn-for example, ones thousands of feet in lengthcan be treated on a continuous basis.

EXAMPLE The invention is further demonstrated by the following illustrative example.

A series of runs were carried out wherein wool yarn was exposed to a plasma, using apparatus as above described. Reaction chamber 1 was a 15 mm. diameter glass tube excited by a Tracer Laboratory PRS-3000 generating and tuning system applying oscillations of 13.56 M Hz. The temperature in chamber 1 was about 50 to 100 C. Tubes 7 and 8 were each about 300 mm. long and I mm. internal diameter. The diameter of the yarn averaged 0.37 mm. The conditions such as power applied, residence time, and pressure were varied as noted below. In some of the runs reaction chamber contained ambient air, in other cases a selected gas was introduced as noted below.

The treated yarns were knitted into fabrics which were then washed with a conventional water and detergent formulation. Measurements taken before and after washing provided the area shrinkage of the fabrics. The same procedure was applied to the untreated yarn to provide a control.

The conditions applied and the results obtained are summarized below.

Treatment conditions Residence area Pressure Power time shrinkage Run Medium mm. Hg. watts sec. 1 Air 2 30 0.6 5.7 2 Air 2 30 0.6 7.0 3 Air 2 50 0.4 7.2 4 Air 2 50 0.6 2.5 5 Helium 3 30 0.6 3.2 6 Helium 25 50 0.6 2.6 7 Helium 50 50 0.4 8.7 8 Nitrogen 3 30 0.6 4.2 9 Oxygen 4 30 0.6 3.0 10 CO 2.5 60 0.6 2.0 II CO, 2.5 60 (L3 8.0 12 NH 2.5 30 0.9 4.2 Control 44 In this run, two yarns were treated at the same time.

The treated yarns and the untreated yarn were also subjected to standard tests for abrasion resistance (ASTM D-l379) and for tensile strength. The results are summarized below.

Abrasion resistance Tensile Product tested cycles to break strength, lbs. Treated yarn 1050-] I00 l.48-l.57 Untreated yarn 700-720 1.20-1.22

Having thus described the invention, what is claimed 1. Apparatus for treating wool yarn with a low temperature plasma, which comprises, in combination a. a reaction chamber made of borosilicate glass,

b. an inlet tube having one end connected to the reaction chamber and the other end open to the atmosphere,

c. an outlet tube having one end connected to the reaction chamber and the other end open to the atmosphere,

d. each of said tubes having an internal diameter sufficiently greater than the diameter of the wool yarn under treatment to permit the latter to slide readily through the tubes and to avoid subjecting said wool yarn to friction, abrasion, or stretching forces,

e. each ofsaid tubes having a length at least times the internal diameter thereof,

f. a first bobbin for storing a supply of wool yarn to be treated, said bobbin being mounted in the open atmosphere and adjacent to the open end of said inlet tube,

g. a second bobbin for storing treated wool yarn, said bobbin being mounted in the open atmosphere and adjacent to the open end of the outlet tube,

h. means for continuously drawing wool yarn from the first bobbin, through the inlet tube, reaction chamber, outlet tube, and onto the second bobbin,

i. means for exhausting the interior of the reaction chamber,

j. means communicating with the inlet and outlet tubes at points spaced from the ends thereof for exhausting air which enters the open ends thereof,

k. a pair of electrodes mounted on the exterior of the reaction chamber,

3,746,858 6 I. a generator for producing an alternating current trodes whereby to excite the reaction chamber with having a frequency in the radio to microwave frethe said high-frequency current and to produce a quency range, and glow discharge therein. m. means connecting said generator with said elec- 

